Comparative assessment of functional properties, free and bound phenolic profile, antioxidant activity, and in vitro bioaccessibility of rye bran and its insoluble dietary fiber

In cereals, 95% of dietary fiber is associated with phenolic compounds. The present study examined the functional properties, phenolic composition, antioxidant activity, and in vitro bioaccessibility of phenolics and flavonoids present in rye bran (RB) and its insoluble dietary fiber (IDF). Compared to RB, higher functional properties (WHC, WRC, and OHC) were represented by IDF due to its porous structure. The IDF contained lower free but higher bound phenolics and flavonoids content as compared to RB, whereas highest total phenolics (556.6 mg GAE/100 g) and flavonoids (378.3 mg RE/100 g) content were observed in IDF. Results had identified significant differences (p < .05) in phenolic acids composition between RB and IDF determined by HPLC-MS and the total phenolic acids were higher in IDF. The antioxidant capacity of IDF was higher than RB in DPPH, FRAP, ABTS, and reducing power assay. However, the in vitro phenolics and flavonoids bioaccessibility of IDF was much lower because of its high content of bound phenolics and flavonoids. PRACTICAL APPLICATIONS: A successful comparative study between RB and its IDF has been conducted in this research work that edifies the health benefits associated with the phytochemicals linked with RB and IDF. The present study also carries rich information regarding the cereal chemistry of RB that truly facilitates the food developers to specifically focus on the bioaccessibility of phenolic compounds present in IDF and RB. The findings about the functional properties and antioxidant capacities of RB and its IDF can also open new research horizons when dealing with food product development tasks, specifically related to therapeutic and medically tailored meals for the targeted customers.

Keywords: antioxidant activity; in vitro bioaccessibility; insoluble dietary fiber; phenolic compounds; rye bran.